The present invention relates to a chain conveyor system and especially the coupling between individual conveyor chain links. The chain link has a link member which has a transport facilitating means, an underside and a lower portion extending downwardly from the underside and the transport facilitating means, the lower portion has means for attaching a plurality of chain links together to form a conveyor belt which is flexible in two dimensions. The lower portion includes a forward portion and a rearward portion, a pin, and a bearing element.
Many conveyor chain links of the prior art accomplish the linking action between links by arrangements comprising two bearing elements, a substantially cylindrical plunge and a pin with a circular cross-section, preferably a steel pin. This assembly constitutes a gimbal joint which is used to obtain multidirectional linking between adjacent chain links, i.e. a freedom of movement in two dimensions.
In U.S. Pat. No. 5,402,880 an article carrying chain is disclosed. The chain is to be used in an article conveyor and it includes a plurality of interconnected moulded plastic chain link assemblies each having a planar top plate. A plurality of upper an lower tabs formed along the lower portions of the chain link assemblies serve to guide the chain relative to a pair of guide rails of the conveyor frame while permitting free removal of the chain link assemblies from the guide rails at selected areas along the length of the conveyor and also restraining the chain between the guide rails at other portions of the conveyor such as at curves or vertical bends. Important features of the linking assembly are the connecting pin, which is arranged between the adjacent links of the chain, and the holes of the link through which the connecting pin is arranged. The hole diameter is considerably larger than the connecting pin diameter enabling the pin to perform a movement relative to the link. Thus, the pin is not fixedly attached to the plunger, i.e. it is allowed to rotate and move in a radial direction of the pin. This has as a consequence the requirement that the connecting pin must be carefully designed in respect of e.g. choice of material of manufacture and it requires a high precision of manufacture.
In U.S. Pat. No. 3,768,631 a conveyor is disclosed which comprises a series of links which directly carry the articles to be conveyed. Each link includes a head portion from which extends a pair of bifurcated legs for receiving and being coupled to the head portion of an adjacent link. The link further comprises a carrier portion that is integral with the head potion and the legs. The upper side of the carrier portion is a continuous flat transport surface overlying the head portion and the legs and the transport surface at one end is defined by the upper periphery of the head portion. The opposite end of the carrier portion is a web interconnecting the legs and having a concave edge corresponding in shape to the periphery of the head portion. The carrier portion further includes a pair of side flange portions which extend longitudinally from the extremities of the legs and laterally to the head portion and which define the longitudinal edges of the continuous flat transport surface. Also this design utilizes a plunger and pin gimbal joint. Thus, this invention requires a carefully designed connecting pin since it is a crucial part if the linking assembly of the invention.
Neither of the arrangements described above disclose a device for limiting/preventing lateral movement between the chain links. Both above patents present inventions in which the interaction of the non-fixed connection pins and its corresponding holes, which have considerably larger dimensions than the pins, is crucial in obtaining a multidirectional linking between adjacent links.
An alternative arrangement to obtain multidirectional linking between adjacent chain links, i.e. a freedom of movement in two dimensions, is by utilizing a ball and socket type joint.
In U.S. Pat. No. 1,996,586 a conveyor is disclosed which comprises a series of chain links which are interconnected by a separate connecting element having concave bearing means which form ball and socket joints together with spheroidal elements arranged at each end of the elongated chain links. No continuous carrying surface is formed using this conveyor construction and all the pulling force transmitted from chain link to chain link will have to be absorbed by the axle holding the spheroidal elements. This axle is an integral part of the chain link and made of the same material as the link. Since the most widely used material for conveyor chains of the above type is plastic, the axle will not be sufficiently strong unless it is made having a sufficiently large cross-section. This results in relatively bulky chain links which are more costly and which require more space when in use. If the connecting element is provided with some sort of flat carrying surface, there is a great danger that the connecting element will turn over when a load is placed on the carrying surface, since it is only held by the two spherical bearings and thus lacks support against turning sideways.
In DE 39 91 247 is shown a conveyor link assembly comprising spherical bearing means. The spherical means 13 is held between the two legs at one end of a link 7 and is circumferred by the trailing link end opposite its leg end. It is not shown how the spherical means is held in its place, only a small axis 11, which seems to be inside another coaxial axis holding a pair of wheels, rolling in guides. How the parts are kept together cannot be seen nor is described. There seems to be a ring which can have a partly spherical inside seat being forced on the spherical element and pressed into the link end. Some sort of frictional and deforming forces have to be overcome, otherwise the parts should fall apart. It is also possible that glue or the like is used. The material of the parts seem to be metallic thus implicating the use of mounting tools. The trailing link end thus circumferes the spherical element without any shown gap, eliminating the risk of play and contact between links, at least when the guides are not twisting. This conveyor link assembly seems to be complicated to assemble with a lot of different parts. Once the problems to have the ring seat put in place around the spherical element and in the link are overcome, the design does not display any problems to keep it there, giving the parts have the proper dimensions.
In U.S. Pat. No. 4,524,865 a conveyor chain is disclosed which comprises a series of links which are interconnected by a ball and socket joint. Each elongate link has a ball element at one end and a socket element at the other, opposite end. When the ball element of a first link has been inserted into the socket element of a second link, a pin is inserted into holes at each side of the socket element so that the pin runs through an elongate hole in the ball element and the two links are held together in the travelling direction of the conveyor chain. The pin is held in the holes by splines formed on the pin at its two ends in order to prevent the pin from getting lose and falling out of the assembly. The pin prevents the ball element from popping out of the socket element during operation of the conveyor. A force working in a direction substantially perpendicular to the travelling direction of the conveyor is generated when the conveyor is in operation and this force will try to remove the ball element from the socket element, thus increasing the power demanded to propel the conveyor. In order to facilitate the insertion of a ball element into a socket element, the socket element can only be formed as partially encompassing the ball element. This results in a relatively small contact surface area between ball and socket in the travelling direction of the conveyor which could lead to breakage of individual links when a higher stress is put upon the chain, e.g. when the conveyor is made to turn in a curve. The whole arrangement is unsymmetrical regarding force distribution, both horizontally and vertically. The ball element and the socket element are made of the same material, since they are part of the same link element. This will result in increased squeaking when the conveyor chain is in operation, when the ball element is moved (rotated) relative the socket element. In addition, with design such as described the carrying surface will protrude excessively from the conveyor belt line when the chain is bent over a driving wheel or the like since the carrying surface is arranged far forward towards and over the ball element of each chain link.
A main object of the present invention is to overcome the above mentioned disadvantages and to provide an improved chain link conveyor having a joint between individual links which allows unrestricted movement of two adjacent chain links at least partially in two dimensions, which is self-adjusting with respect to the main guidance bearing surfaces, which allows a relative twisting movement between adjacent links in a direction perpendicular to the normal travelling direction of the chain link conveyor allowing the chain link conveyor to be twisted in a screw-like motion around its direction of travel, and which is strong and yet simple and cheap to manufacture.
A further object of the invention is to provide a ball and socket joint between individual links in which relative movement between adjacent links in a direction perpendicular to the normal travelling direction is minimized, which results in decreased or eliminated squeaking.
A still further object of the present invention is to provide a design of the ball and socket joint which can transmit a force in both forward and backward travelling directions of the conveyor.
This object is achieved in a conveyor system comprising a conveyor chain, a chain guidance means and a guide support means where said conveyor chain comprises a plurality of chain links, each link comprising a link member (2), a connecting pin (7) and a bearing element (8), where said link member has a cargo carrying means (20) and a lower link member portion (3) having a first end (4) and a second end (5), said second end having a first leg (11) and a second leg (12) arranged at a certain distance from each other, where said first leg has a first through hole (9), and said second leg has a second through hole (9xe2x80x2) substantially coaxial with said first through hole (9), said first through hole (9) and second through hole (9xe2x80x2) being arranged to hold said connecting pin, and where said bearing element is substantially spherical and has a third through hole (9xe2x80x3) being arranged to hold said connecting pin, and said first end has a substantially spherical bearing seat (10) arranged to cooperate with at least a part of the surface of said spherical bearing element of an approximate chain link. The new and inventive introductions are that said bearing element (8) further has a first protruding section (31) and a second protruding section (32) adjacent to the two openings of said third through hole (9xe2x80x3), said two protruding sections being arranged to directly contact said first and second leg (11, 12) of said second end (5) of said link member (2) so that said two legs can only be bent towards said bearing element (8) up to said protruding sections.
Another new feature is that said spherical bearing element (8) further has a force absorbing means (15) extending toward an adjacent chain link and that said second end (5) of said link member (2) has a curved surface (16), where said force absorbing means and said curved surface cooperate to transfer the compression forces, generated when said conveyor is made to travel in a second travelling direction opposite to said first travelling direction, from one conveyor chain link to an adjacent conveyor chain link.
The chain guidance means generally consist of a conveyor frame having profiled guide rails arranged on at least two opposite sides of the conveyor chain. The guide rails define the conveyor chain path by allowing slide bearing surfaces on the chain links to slide on the guide rails whilst the chain links are held in a predetermined spacial position relative to each other and to the conveyor chain path. The cargo load is mainly transferred from the chain links to the conveyor frame via the slide bearing surfaces on the chain. Typically, the guide rails are made of extruded aluminium profiles. The guide support means are mounted to the guide rails to keep them in a fixed position relative to a floor or the like and typically consist of height adjustable metal legs.
Features of the invention are that said bearing element consists of a means incorporating a substantially partially spherical element connected to said shaft, said bearing element being connected to said shaft, said rearward portion defining two legs and being provided with transverse first and second holes at a distance from the forward portion, said first and second holes being intended to receive said pin provided with said bearing element, said bearing element being arranged between said legs, said forward portion having a spherical seat arranged to receive said bearing element thereby partly embracing the bearing element, the engagement between said spherical seat and the spherical element of a bearing element of an adjacent conveyor chain link being arranged to accomplish a multidirectional linking assembly, the width of said bearing element being substantially the same as the free space between the legs in the area of said first and second holes.